1. Field of the Invention
The present invention relates to a medical X-ray imaging system.
2. Related Background Art
In medical X-ray photography, in recent years, instead of X-ray sensitive films, X-ray imaging systems using X-ray image pick-up devices have been widely used. Such an X-ray imaging system is convenient such that unlike the X-ray photosensitive film, development is not necessary, and an X-ray image can be confirmed in real time, and is also superior in terms of data storage stability and handling easiness. In X-ray photography for dental diagnosis, such X-ray imaging systems have been increasingly used in various imaging modes for panoramic radiography, cephalometric radiography, and CT.
In the case of a dental X-ray imaging system, the shape of an imaging region required for the X-ray image pick-up device may differ depending on various imaging modes described above. In other words, an imaging region to be used for CT (hereinafter, referred to as a first imaging region) is required to have a sufficient width in the lateral direction, and also required to have a certain width in the up-down direction. An imaging region to be used for panoramic radiography or cephalometric radiography (hereinafter, referred to as a second imaging region) is required to have a sufficient width in the up-down direction. However, when a plurality of X-ray image pick-up devices satisfying these requirements are prepared, the X-ray imaging system becomes large in size, or when changing the imaging mode, the X-ray image pick-up device must be changed and this is troublesome. Therefore, preferably, the requirements on the first and second imaging regions are satisfied by one X-ray image pick-up device.
For example, in International Publication No. WO2006/109808, an X-ray image pick-up device for dental diagnoses having an X-ray generator and an X-ray detector is disclosed. In this X-ray image pick-up device, to selectively generate an X-ray slit beam and an X-ray broad beam, an X-ray is irradiated via a narrow-groove-like slit or a rectangular slit. The X-ray slit beam is used for panoramic radiography or cephalometric radiography, and the X-ray broad beam is used for CT, etc. WO2006/109808 describes that both of the X-ray slit beam which passed through the narrow-groove-like slit and the X-ray broad beam which passed through the rectangular slit are imaged by one solid-state image pick-up device.
As a solid-state image pick-up device to be used for such a medical X-ray imaging system, solid-state image pick-up devices using the CMOS technique are known, and among these, a solid-state image pick-up device using a passive pixel sensor (PPS) type is known. The solid-state image pick-up device using the PPS type has a photodetecting section which includes PPS-type pixels including photodiodes for generating charges corresponding to incident light intensities are two-dimensionally aligned in M rows and N columns, and accumulates charges generated in the photodiode in response to light incidence on each pixel into a capacitive element in an integrating circuit, and outputs a voltage value corresponding to the accumulated charge.
Generally, output terminals of the M pixels in each column are connected to an input terminal of the integrating circuit provided corresponding to the column via a reading wire provided corresponding to the column. Charges generated in the photodiodes of the respective pixels are input into the integrating circuit through the reading wires corresponding to the relevant column from each row successively from the first row to the M-th row, and from the integrating circuit, a voltage value corresponding to the charges is output.